The invention relates generally to the field of optical telecommunications, and more specifically to MEMS actuators for positioning optical mirror elements.
The emergence of high-speed optical data communication networks with their associated routing and reconfiguration requirements has created a need for high-speed, high-bandwidth fiber-to-fiber switching systems. Switching of data from one fiber to another typically utilizes an optical-to-electrical input stage, an electronic switching matrix, and an electrical-to-optical output stage, referred to as optical-electrical-optical (OEO) conversion. With the advent of dense wavelength division multiplexing (DWDM), a single optical fiber may contain data streams on one to 160 or more different channels operating at predefined optical wavelengths. Switching this large number of channels with increasingly higher data rates places large demands on OEO switch configurations, requiring many components, higher power consumption, and large cabinetry to house the equipment. Furthermore, with an increasing number of input fibers and output fibers in such systems, compact, accurate, and rapidly reconfigurable alternatives are needed to meet the demand for compact, high-performance fiber optic switches in single-mode and multimode optical networks.
Opto-mechanical switches may meet these demands by using optical mirror elements that are actively positioned to guide one or more beams of light from each input fiber to one of potentially thousands of output fibers in long-haul and metropolitan telecommunication networks. Use of mirrors eliminates the need for OEO conversions in many cases, because an accurately positioned mirror may readily redirect light from a selected input fiber to a selected output fiber. An optomechanical cross-connect system, however, may require a large number of mirrors and associated actuators for positioning the mirrors. The mirrors and actuators need to be accurately and tightly configured to accommodate large port-count switches in a compact environment.
One solution to small and large port-count switches utilizes microelectromechanical systems (MEMS) devices, fabricated using high precision and highly replicable processes similar to those used in semiconductor manufacturing. Aspects of these systems are described, for example, in xe2x80x9cOptical Mirror System with Multi-Axis Rotational Control,xe2x80x9d U.S. Pat. No. 6,283,601 by P. M. Hagelin, et al., issued Sep. 4, 2001.
Mirror elements used in optical switching systems may be a scanning type, which is able to tilt an optical mirror about one or two axes to redirect a beam of light. Other approaches include a pop-up or switching mirror that interrupts and re-directs a beam of light into a specific output port, requiring at least one mirror for each output fiber, replicated for each input port.
Scanner-based mirror systems capable of redirecting light from one input port to one of many output ports may use only a single or perhaps two scanning mirrors per port. To accommodate large port counts, the scanning mirrors may require large tilt angles exceeding ten degrees about one or two degrees of freedom.
Positioning or tilting the mirrors requires accurate, compact microactuators that are fast, reliable and use low power, while providing large tilt angles with multiple-axis rotational control. The actuator and mirror assemblies should be constructed with high precision while avoiding the need for post-assembly. The actuators should provide large deflections to position the mirror, generate large forces and operate with low voltages and low power. The actuators should be strong, lightweight, compact, and readily scalable. The actuators and mirror assemblies would preferably be built using a process that provides high repeatability, affordability and scalability.
It is an object of the present invention to provide an actuator for micropositioning applications such as steering a beam of light, by overcoming the barriers and obstacles described above.
An actuator for steering a beam of light in accordance with the present invention is disclosed. The actuator may include a rotatable actuator member coupled to a substrate, a movable portion of an actuator drive mechanism coupled to the rotatable actuator member, a balancing spring coupled between the substrate and the movable portion of the actuator drive mechanism, and an actuator arm coupled to the movable portion of the actuator drive mechanism. During actuation, the actuator arm may be rotated while the balancing spring maintains the movable portion of the actuator drive mechanism essentially parallel to the substrate. Among the types of drive mechanisms that may be used with the actuator are a thermal drive mechanism, a piezoelectric drive mechanism, a magnetic drive mechanism, and various electrostatic drive mechanisms including a parallel-plate electrostatic drive mechanism and an interdigitated electrostatic drive mechanism.
The actuator of the present invention may be part of an optical subassembly that may direct or steer at least one beam of light using an optical mirror element. The optical mirror may be coupled to at least one counterbalanced actuator. The mirror may be positioned at a desired height and tilt angle using the counterbalanced actuators.
A method of actuating a micromirror assembly including at least one counterbalanced actuator and a mirror element may include the steps of applying a first control voltage to a movable portion of a counterbalanced actuator; applying a second control voltage to a fixed portion of the counterbalanced actuator; positioning a micromirror coupled to the counterbalanced actuators; and directing a beam of light with the micromirror.